Sains Malaysiana 47(11)(2018): 2677–2683

http://dx.doi.org/10.17576/jsm-2018-4711-10

 

Rapid Microbial Detection Model System in UHT Milk Products using Poly(L-Lactic Acid) (PLLA) Thin Film

(Sistem Pengesanan Mikrob Model Pantas di dalam Produk Susu UHT menggunakan Filem Nipis (PLLA) Poli (Asid L-Laktik))

NURUL HIDAYAH YUSOF, NORRAKIAH ABDULLAH SANI, FARAH HANNAN ANUAR, MOHD SUZEREN JAMIL & SAIFUL IRWAN ZUBAIRI*

 

Centre for Biotechnology & Functional Food, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

 

Diserahkan: 9 Februari 2018/Diterima: 17 Julai 2018

 

ABSTRACT

Ultra-high temperature is a process that involves heating of milk to a very high temperature to produce sterile milk products. However, food poisoning due to consumption of UHT milk still happen in Malaysia. This study was done to develop a film that is made by poly(L-lactic acid) (PLLA) to detect the presence of microorganisms in UHT milk products. UHT milk that was used in this study was full cream milk. Contaminated milk that contained Bacillus cereus was made to conduct a model system on the relationship between colony forming unit of microorganisms and contact angle. Contaminated milk was also used as a control sample to study the difference of milk properties between fresh and contaminated milk. Physicochemical analysis (Brix, colour, pH and contact angle) and microbiological analysis (total plate count) were done to UHT milk sample as soon as the packaging of the milk was unsealed. Analysis was done with 30 min time interval until 4 h and 30 min since the unsealing of packaging. The results showed that presence of microorganisms in UHT milk was detected after the milk product was unsealed and exposed to environment for 3 h and 30 min. Contact angle resulted from the presence of microorganisms in UHT milk was 64.34 - 65.44° with its colony forming unit, 2.1 – 3.9 cfu/mL. Therefore, the potential usage of contact angle on PLLA thin film with respect to colony forming unit (cfu) in detecting the presence of microorganisms in UHT milk product was attained and well modelled.

 

Keywords: Contact angle; microorganisms; PLLA; spoilage indicator; UHT milk

 

ABSTRAK

Rawatan suhu ultra-tinggi merupakan proses yang melibatkan pemanasan susu kepada suhu yang amat tinggi bagi menghasilkan produk susu yang steril. Walau bagaimanapun, keracunan makanan akibat pengambilan susu UHT masih berlaku di Malaysia. Kajian ini dijalankan untuk membangunkan satu filem yang diperbuat daripada PLLA bagi mengesan kehadiran mikroorganisma dalam produk susu UHT. Susu UHT yang digunakan dalam kajian ini adalah susu krim penuh. Susu terkontaminasi yang mempunyai Bacillus cereus dihasilkan untuk menjalankan sistem model berkenaan hubungan antara unit pembentukan koloni mikroorganisma dengan sudut sentuh. Susu terkontaminasi juga digunakan sebagai sampel kawalan untuk mengkaji perbezaan sifat susu bagi susu segar dengan susu terkontaminasi. Analisis fizikokimia (Brix, warna dan sudut sentuh) dan analisis mikrobiologi (hitungan piring jumlah) dijalankan ke atas sampel susu UHT sebaik sahaja selepas pembungkusan susu dibuka. Analisis dijalankan dengan sela masa 30 min sehingga selepas empat jam dan 30 min pembungkusan dibuka. Keputusan menunjukkan kehadiran mikroorganisma dalam susu UHT dikesan selepas produk susu dibuka dan didedahkan kepada persekitaran selama tiga jam dan 30 min. Sudut sentuh yang dihasilkan akibat kehadiran mikroorganisma dalam produk susu UHT adalah 64.34 - 65.44° dengan unit pembentukan koloni, 2.1 - 3.9 cfu/mL. Oleh yang demikian, potensi penggunaan sudut sentuh pada permukaan filem nipis PLLA terhadap unit pembentukan koloni dalam pengesanan mikroorganisma di dalam produk susu UHT telah diperoleh dan dimodelkan dengan berkesan.

 

Kata kunci: Indikasi kerosakan; mikroorganisma; PLLA; sudut sentuh; susu UHT

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*Pengarang untuk surat-menyurat; email: saiful-z@ukm.edu.my

 

 

 

 

 

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